Control device



March 16, 1943. E, H, AYERS CONTROL DEVICE Filed July 1, 1941 1 2 Sheets-Sheet 1 Inventor: I Edgar H. A ers,

i-"Hs Attorne g Mar-ch16, 1943. E. H. AYERS 2,314,191

CONTROL DEVICE 2 Sheets-Sheet 2 Inventor:

b g 77 M767 (7 4 Edg av H, A ears.

His Attorne g.

Patented Mar. 16, 194.3

common nnvron Edgar H. Ayers, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application July 1, 1941, Serial No. 400,632

18 Claims.

My invention relates to control devicesv and more particularly to refrigerator control devices, and has for its object a simple and reliable device provided with a single knob for adjusting the device for a desired refrigerator temperatureand for adjusting the device to provide a high defrost temperature after which the control is returned to a normal operating condition, and in addition, to give a single cycle low temperature quick-freeze setting after which the control is returned to the normal operating condition.

More specifically,.my invention relates to control devices utilizing over-center spring snapping means of the type described and claimed end a movable contact l3 which cooperates with a stationary electric contact I. This switch arm is actuated by an operating arm i5 having a pivot i6 and operated by a bellows temperature responsive device IT. The over-center spring connection between these two arms ID and I5 comprises a U-shaped link I8 having its ends pivotally secured on a pivot 20 on the ends of two laterally extending projections 19 which are spaced apart and secured to the end of the operating arm {5. The cross or base portion 21 of the link is connected, by an over-center helical in Patent No. 1,921,126, issued on August 8, 1933,

to Leonard P. Hutt. In carrying out my invention, I provide means operated by a single knob for temporarily moving the switch arm to predetermined positions for the defrost and quick freeze settings in which the position of the point of connection between the over-center operating spring and the switch arm is changed so as to require a larger or smaller movement of the operating member to produce snap action of the switch arm. After operation of the control at this high defrost or low quick freeze temperature, the latching means is disengaged forceably by the operation of the switch arm by the overcenter spring.

For a more complete disclosure of my invention, reference should be had to the accompanying drawings in which Fig, 1 is a plan view of a control device having means for obtaining a defrost adjustment embodying my invention; Fig. 2 is a partly sectional view along the line 2-2 of Fig. 1 looking in the direction of the arrows; Fig. 3 is a view in perspective of the operating mechanism alone with certain parts distorted for purposes of clarity; Figs. 4 and 5 are fragmentary views of the stop means in the normal open and defrost open positions respectively; Fig. 6 is a perspective view similar to Fig. 3 showing a form of my invention providing for both defrost and quick freeze settings; Fig. '7 is a view similar to Fig. 6 showing a modified form of my invention having a defrost setting only; while Fig. 8 is an exploded view in perspective and partially in section of an operating knob embodying my invention.

Referring to the drawings, in one form of my invention I provide over-center spring snap operating means for the switching means comprising a switch arm l0 secured on a pivot II and provided with a flexible arm l2 carrying on its tension spring 22 with a projection 2211 on the end of the switch arm I0 and extending laterally therefrom. This projection 22a is positioned to move between the projections 19 upon relative movement between the two arms I0 and i5. Stops 24 and 25 are provided on opposite sides of the link l8 adjacent its closed movable end for the purpose of limiting the movement of this end,

In the operation of this over-center snap mechanism, the determining factor is the relative positions of the pivot 20 and the pivot 23 forming the connection between the spring 22 and the projection 22a. When the pivot 20 is below the pivot 23, as viewed in Fig. 1, the spring applies a force holding the link l8 against the upper stop 24 and a force to the arm 10 biasing it in a counterclockwise direction so as to hold the contact I3 in engagement with the contact l4. If now the arm I5 is raised, as viewed in Fig. 1, until the pivot 20 is slightly above the pivot 23, then the spring. applies a component of force tending to move the link I8 clockwise about its pivot 20 into engagement with the lower stop 25. This, of course, changes the position of the end of the spring and thereby reverses its component applied to the arm Ill. As seen in Fig. 1, the spring applies a force along a line passing through the pivot 23 and extending above the pivot i 1. Soon after the link l8 beginsto move downward the line of force of the spring moves below the pivot ll whereby a counterclockwise torque is applied to the arm 10 and the arm istherefore snapped in a counterclockwise direction to its open circuit position.

In accordance with myinvention, I provide means for temperarily moving the arm ill to a position in which the position of the pivot 23 is changed thereby to vary therequired amountoi movement of the arm ii to snap the switch arm to its open or closed circuit position, as the case may be. As a result, a higher or lower temperature is required to cause the bellows I! to actuate the operating arm.

In the form of my invention shown in Fig. 1 I provide an extension 26 on the switch arm l extending laterally therefrom and downwardly, as viewed in Fig. 1. On its end this extension 26 is provided with a lateral extension 28a extending behind the bellows spring adjusting screw 21, as viewed in Figs. 1 and 2, where it is bent laterally downwardly to provide a portion 26b substantially parallel with the main portion 26 of the extension. This portion 26b extends through an aperture 28 provided for it in the enclosing casing 29 for the mechanism into cooperative relation with a knob 30 secured on the end of the adjustment screw 21. Thus by turning the knob 30 in a counterclockwise direction, as viewed in Fig. 3, an abutment or projection 3| on the knob is brought into engagement with the projection 26 and the projection is thereby' moved toward the right hand, as seen in Figs. 1 and 3, whereby the switch arm I8 is moved in a counterclockwise direction about its pivot Ii to its open circuit position with the contact l3 disengaging the contact 14.

I provide resilient stop means for defining the position of the switch arm in this open circuit position. This stop means comprises a spring strip 32 secured to the portion 26a in lengthwise parallel relation therewith. Preferably, it is secured to the portion 26a at its lefthand end 33 as by riveting-so that the remaining length of the strip is free to flex away from the portion 26a. The end of the strip 32 is moved to abut against a stop portion 34 provided by a bend in a spring strip member 35 when the knob 30 is turned to its extreme counterclockwise position. This is the defrost open position of the switch arm, although the knob must be moved back clockwise somewhat in order to free the end 26b and permit reclosure of the contacts by the bellows. Ordinarily, during normal operation of the device with the knob in an intermediate position, the end of the strip 32 abuts against the end portion 36 of the spring latching member 35 when the switch arm I0 is in its open circuit position, as shown in Fig. 4. The spring arm 35 thus limits or defines these normal and defrost open circuit positions.

When the knob 30 is thus turned to its extreme counterclockwise position, the strip 32 pushes the strip 35 aside toward the right hand, as viewed in Figs. 1 and 3, while at the same time the end of the strip 32 slides upward along the portion 36. Eventua ly the end of the strip 32 moves upward far enough to disengage the portion 36 and it then moves toward the right hand into engagement with the stop 34 on the strip 35 as seen in Fig. 5. The switch arm is now in a position in which the pivot 23 is lower, as seen in Fig. 1, than the normal open circuit position of the pivot and. therefore, the operating arm I5 must be moved downward a greater distance than normally in order to bring the pivot 20 below the pivot 23 and cause the link I8 to snap upward to the position shown in Fig. 1 for reclosure of the switch arm.

It will thus be observed that the spring 22 must be strong enough to snap the switch arm against the opposing force offered by the end of the strip 32 and force the end of the spring 32 over the shoulder 36a at the top of stop 36 back to the position of Fig. 4. In order to effect this the strip 32 is made much weaker than the snapping force applied by the spring 22. Also this is effected 32 with the portion 26a whereby flexure'of the strip 32 in a downward direction as seen in Fig. 1 is limited mainly to the small portion projecting beyond the portion 26a. This portion is stiff enough to push the spring strip 35 away slightly with little bending of the strip 32 when the strip is moved to the defrost position of Fig. 5. This gives precision in the setting of the two parts for the defrost adjustment. On the other hand, the entire strip 32 is free to flex in moving from the position of Fig. 5 to the position of Fig. 4 and the strip is made fragile enough with respect to the spring 22 so that the strip readily bends.

Not only must the bellows compress the spring 31 farther from the defrost adjustment, but the operating arm l5 engages an auxiliary spring arm 38 mounted on the pivot l6 and biases against a stop 39 by a helical compression spring 40. This arm 38 has the projection 4| extending to a point near the arm l5 but normally not engaged by the arm l5. When. the defrost setting is made, however, the arm l5 must be depressed far enough to engage the projection 4| and thereafter compress the auxiliary spring 40 in order to snap the switch arm to the closed position. This additional load of the spring 40 requires higher fluid pressures in the bellows and, consequently, a higher temperature for operation, which temperature is high enough to effect the defrosting of the evaporator'.

It is contemplated that the bellows is responsive, through the usual closed tubular system containing an expansible fluid, to the temperature of the evaporator in a well known manner.

It will be understood that the adjustment screw 2'! is provided with a coarse thread having sufficient pitch to give the desired range of adjustin part by the lengthwise engagement of the strip ment of the bellows spring 31 in less than one complete revolution of the screw. It will be noted that the lower end of the spring 3'! rests on a traveling seat 42 with which the screw is in threaded engagement. This seat is provided with two spaced prongs 43 (Fig. 3) which embrace a rib on the inner wall of the casing extending parallel with the screw whereby the seat is held against turning movement. Moreover, the pitch of the screw threads is preferably in such direction that movement of the knob for the defrost setting compresses the spring 31 to its fully compressed position although the spring pressure is relieved somewhat when the knob is turned back to release the projection 26b after making the defrost setting. The knob may be left, however, if desired, in its extreme counterclockwise position, in which position the contact arm I0 is held permanently in its open circuit position whereby operation of the refrigerator motor controlled by the contacts and cooling of the refrigerator is prevented.

As seen in Fig. 1, a suitable connection terminal 44 is provided for the stationary contact Hi, the two being connected together by a suitable screw or rivet. Also, a connection screw 45 spaced from the screw 44 is provided for the movable contact l3. This terminal 45 is connected to a rigid electrical conductor 43 inside the casing which, in turn, is electrically connected by means of a flexible lead 41 to the contact arm H).

In the form of my invention shown in Fig. 6 I

with Figs. 1 to 5 inclusive by means of the sprin latching members 53 and 54. Th operating connection between the plunger 50 and the switch arm 52 is made by means of a disc 55 secured to the plunger 56 and being free to turn with the knob 5|. This disc lies in a notch 56 in the end of the arm 52, the notch being several times wider than the disc so as to provide a limited freedom of movement. Thus the plunger 50 can be pressed to establish the defrost setting when the knob is in any angular position. When the plunger is pressed, the disc 55 engages the innermost edge of the notch 55. Also, if desired, the defrost setting can be cancelled by pulling the plunger out until the strip 52 is pulled off the latch strip 54 by engagement of the disc with the outermost dge of. the slot 55.

The quick freeze adjustment is efiectedby pull ing the plunger 50 out still farther, i. e., farther than required to cancel the defrost setting. This pulls the switch arm 52 outward, as seen in Pg 6, and moves the switch arm about its pivot 51 in a clockwise direction slightly, whereby it becomes necessary for the operating arm 58 to be moved a greater distance clockwise about its pivot 59 in order to separate the contacts, and consequently the motor driving the refrigerator mechan sm opcrates to reduce the refrigerator temperature to a still lower value until the bellows spring 60 overcomes the bellows and moves the operating arm 58 to operate the contacts.

The switch arm is held in this quick freeze position by means of an extension 6| secured to it and carrying at its end a resilient spring strip 52 which is similar to the spring strip 53.. The end of this strip 52 normally, as shown in Fig. 6. rests in abutting relation against the end of a flexible spring contact arm 63 carrying a movable contact 54'on its end. During the quick freeze adjustment the end of the strip 62 moves toward the left hand, as seen in Fig. 6, moving the end of the contact arm 53 to one side until finally the end of the strip 62 slips over a latching shoulder '65 in the strip 63. against this offset longer portion as a stop. This is the quick freeze position.

It will be noted that in this form of the invention the movable contact is not secured directly on the arm 66, as shown in Fig. 1. but constitutes a separate arm 53 having one end secured to a fixed electrically conducting support 61. The normally stationary contact 6 8 is likewise on the end of a flexible arm 69 secured to an electrically conducting support 10. The supports 61 and 16 are secured in the electrically insulating casng-described in connection with Fig. 1 and constitute means for connecting electric leads to the contents and 58. It will be understood that the arm 69 yields with the arm 63 when the quick freeze adjustment is being made.

It will be understood that th quick frerze adjustment, since it is for a lower temperature than prevailing at the time the adjustment is made. will eifect the engagement of the contacts 66 and 68, if they are not already engaged.-- for operat'en of the refrigerator unt l a low temperatu e is reached. When the low temperature is reached. the over-center snapping spring 1| snaps the switch arm to its open circuit positon and in doing so exerts enough force to forceably pull the end of the strip 62 off the shoulder 65 and thereafter move the end of the strip 52 away from the contact arm 53 whereupon the contact arm moves its contact 64 out of engagement with the oher contact to open the motor circuit. It will be understood that the contact arm 65 is shaped or bent so as to normally assume a position with its contact 64 in spaced relation with the other I contact.

' defrost and quick freeze respectively. Thus the spring12 normally holds an arm 14 in the position shown about its pivot 15 with one projection 16 in engagement with a stop member 11. Another projection 18 of this arm 14 is in position to be engaged by the end of the operating arm 58 when it is depressed during defrosting and thereby applies an additional spring force to the operating arm 19 in the position shown about the pivot 15 r with one projection in engagementlwith the stop 11 and another projection 8| in a predetermined position on the opposite side of the operating arm from the projection 18. Therefore, when the operating arm 58 is moved clockwise during quick freeze beyond its normal position for opening of the contacts, it engages the projection 8| and the pull of the spring 13 is applied to it. It will be noted that the spring 13 acts in opposition to the main bellows spring 82 in this case, thus reducing the effective spring force tending to move the operating arm clockwise. As a result, a lower temperature is required to separate the contacts.

Another feature of the springs 12 and 13 is that their two ends opposite their ends which are secured to the arms 14 and 19 are secured to an extension 83 carried by the seat member 84 from the spring 60. Thus, when the knob 5| is rotated to vary the pressure of the spring 60' and thus adjust the temperature maintained in the refrigerator, the pulls applied by the springs 12 and 13 to their arms are adjusted accordingly but .in inverse relation to the adjustment of the compression spring 60. In other words, movement of the adjustment member 84 to compress the spring 60 and thereby increase the pressure applied by the spring 66 at the same time decreases the lengths of the tension springs 12 and 13 whereby theforces applied by them are decreased. This inverse adjustment of the springs 12 and 13 is such that the spring pressure opposing the operating arm 58 during defrost and quick freeze is always a substantially predetermined value regardless of the temperature setting of the refrigerator. a

It will be observed, furthermore, that the disc 55 is provided with a radially extending projection 85 on its periphery which provides for an off position in which the contacts are permanently separated. This off position is obtained by turning the knob 5lsubstantially from the position shown in Fig. 6 until the projection 85 engages the switch arm 52 and forces it to its open circuit position. Also, a notch is provided in the disc 55 adjacent the projection 85 to facilitate the assembly of the parts. this notch being deep enough to permit the'end of the switch arm 52 to he slipped through itto the position shown in Fig. 6. i

The modified form of my invention shown in Fig. 7 is similar to the form shown in Figs-1 to 5 inclusive in that an adjustment for defrostonly is provided. It utilizes, however, the plunger 50 of Fig. 6 together with the adjustment disc 55. In this form of Fig. 7, also, the compensating spring 51 is secured to the adjustment member stood from the description in connection with- Fig. 6.

As shown inFig. 8, the plunger 50 is provided with an internal opening for -a helical compression spring 95 and with slots Sli'and 91 in which loosely fit radially extending arms 98 and 99 on the knob 5|. This arrangement secures against rotation the hub portion I00 of the knob to its outer cylindrical portion while providing for relative axial movement between the two. On the opposite side of the arms 98 and 99 from the plunger is a second compression centering spring I01, the other end ofwhich bears on the disc 55. The disc is secured to the plunger by means of three connecting members I02, I03 and I extending laterally from the disc and spaced 120 apart. The ends of these members are T-shaped and lie in T-shaped slots I95 provided for them in the plunger. Thus the plunger is normally held in a predetermined central position by the springs 95 and I III and may be pushed in or pulled out for predetermined distances.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A control device comprising a switch member, an operating member, a resilient connection between said members for moving said switch member quickly between an open circuit position and a closed circuit position upon a predetermined amount of movement of said operating member with respect to said switch member, stop means for normally limiting the movement of said switch member in one of said positions, means providing for movement of said switch member beyond said one position thereby to require a greater movement of said operating member to cause movement of said switch member, and resilient means engaged by said operating member when said operating member moves beyond said one position for increasing the required pressure by said operating member for operation of said switch member.

2. A control device comprising switching means, a switch member for operating said switching means, a temperature responsive operating member, a spring connection between said members for snapping said switch member between an open circuit position and a closed circuit position when said operating member is moved to predetermined positions with respect to said switch member in response to predetermined changes in temperature, stop means normally limiting the movement of said switch member in one of said positions, manually operated means for moving said switch member past said stop means thereby to require an increased movement of said operating member to snap said perature change for operation or said switch member.

3. A control device comprising a switch arm, a temperature responsive operating arm, an overcenter snap spring, a pivot bearing on each of said arms, connections between said spring and said arms including said pivot bearings whereby the force of said spring is applied to said pivot bearings and the component of the force of said spring producing movement of said switch arm being reversed upon a predetermined amount of movement of said operating arm with respect to said switch arm thereby to move the pivot bearing on said operating arm from one side to the other of the pivot bearing on said switch arm, resilient stop means, a stop member on said switch arm normally engaging said stop means thereby to limit the movements of said switch arm to normal open circuit position, and manually operated means for engaging and moving said switch arm past said stop means beyond one of said positions thereby to require an increased change in the temperature of said operating arm for movement of its bearing to the other side of the bearing on said switch arm, said stop member thereafter engaging said stop means upon a subsequent movement of said switch arm in said open circuit direction thereby to limit the opening movement of said switch arm to a normal open circuit position.

4. A control device comprising a switch arm, a temperature responsive operating arm, an overcenter snap spring, a pivot bearing on each of said arms, connection between said spring and said arms including said pivot bearings whereby the force of said spring is applied to said pivot bearings and the component of the force of said spring producing movement of said switch arm being reversed upon a predetermined amount of movement of said operating arm with respect to said switch arm thereby to move the pivot bearing on said operating arm from one side to the other of the pivot bearing on said switch arm, stop means for limiting the movements of said switch arm to normal open and closed circuit positions, and manually operated means for engaging and moving said switch arm past said stop means beyond one of said positions thereby to require an increased movement of said operating arm for movement of its bearing to the other side of the bearing n said switch arm, and loading means engaged by said operating arm during such increased movement of said operating member so as to increase the temperature change required for operation of said switch arm.

5. A control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement of said operating member in response to an increase in temperature, resilient stop means for limiting normally the movement of said switch member in one direction to a predetermined normal position, said stop means being arranged to yield to provide for movement of said switch member past said stop means beyond said normal position to an abnormal position in which increased movement of said operating member is required to snap said switch member to the other normal position, and a manually operated member for engaging and moving said switch member past said stop means to said abnormal position so that an increased movement of said operating member is required to snap said switch member to its other normal position, said switch member thereafter engaging said stop means upon a subsequent movement of said switch member in said one direction.

6. A control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement of said operating member in response to an increase in temperature, resilient stop means for limiting normally the movement of said switch member in one direction to a predetermined normal position, said stop means.being arranged to yield to provide for movement of said switch member beyond said normal position to an abnormal position in which increased movement of said operating member is required to snap said switch member to the other normal position, a spring opposing movement of said operating member, a manually operated member for varying the force applied by said spring, mean operated by said manually operated member for engaging and moving said switch member past said. stop means to said abnormal position, and auxiliary spring means engaged by said operating member when said operating member is moved through said increased movement to snap said switch member from said abnormal position to the other normal position.

7, A refrigerator control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement of said operating member in response to an increase in temperature, resilient stop means for limiting normally the movement of said switch member in an open circuit direction to a predetermined normal open circuit position, said stop means being arranged to yield to provide for movement of said switch member beyond said normal open circuit position to an abnormal open circuit position in which increased movement of said operating member is required to snap said switch member to said closed circuit position, a spring opposing movement of said operating member in response to an increase in temperature, a manually operated member for varying the force applied by said spring, means operated by said manually operated member for engaging and moving said switch member past said stop means to said abnormal position when said manually operated member is moved to a position of increased spring force, and auxiliary spring means engaged by said operating member when said operating member is moved through said increased movement to snap said switch member from said abnormal open position to said closed circuit position.

8. A control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members for causing said switch member to snap between normal closed and normal open circuit positions upon movement of said operating member, resilient stop means for limiting selectively the movement of said switch member in one direction to one of said normal positions and to an abnormal position beyond said normal position, a spring opposing movement of said operating member, a knob connected to vary the force applied by said spring upon rotation of said knob, means operated by said knob when said knob is turned to a predetermined position for moving said switch member to said abnormal position, and auxiliary spring means engaged by said operating member when said operating member is moved to snap said switch member from said abnormal position.

9. A control device comprising a switchmember, a temperature responsive operating member, a spring forming an operating connection between said members for causing said switch member to snap between closed and open circuit positions upon movement of said operating member, stop means for limiting selectively the movement of said switch member to a normal open circuit position and an abnormal open circuit position, a spring opposing movement of said operating member in response to an increase in temperature, an adjustment member connected to vary the force applied by said spring upon rotation of said adjustment member, a projection on said adjustment member, an extension on said switch member in position to be engaged by said projection when said adjustment member is turned to a position of maximum force applied by said spring thereby to snap said switch member to said abnormal open position.-

10. A control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members for causing said switch member to snap from an open to a closed circuit position upon movement of said operating member in response to an increase in temperature, resilient stop means for limiting selectively the open circuit position of said switch member to a normal open circuit position and an abnormal open circuit position, a spring opposing movement of said operating member in response to an increase in temperature, a knob connected to vary the force applied by said spring upon rotation of said knob, a projection operated by said knob, an extension on said switch member in position to be engaged by said projection when said knob is turned to a position of maximum force applied by said spring thereby to move said switch member to said abnormal open position, and auxiliary spring means engaged by said operating member when said operating member is moved to snap said switch member from said abnormal open position to said closed circuit position.

11. A refrigerator control device comprising switching means, a switch arm for operating said switching means, a temperature responsive operating arm, an over-center spring forming an operating connection between said arms for causing said switch arm to snap between closed and open circuit positions upon movement of said operating arm, resilient stop means for limiting normally the movement of said switch arm to a normal open circuit position and yielding to provide for continuedmovement of said switch arm to a defrost open position, a spring opposing movement of said operating arm in response to an increase in temperature, a knob connected to varythe force applied by said spring upon rotation of said knob, a projection on said knob, an extension on said switch arm in position to be engaged by said projection when said knob is turned to a position of maximum force applied by said spring thereby to snap said switch arm to said defrost open position, and auxiliary spring pressed means engaged by said operating arm when said arm moves to snap said switch arm from said defrost open position to said closed circuit position.

12'. A refrigerator control device comprising switching means, a switch arm for operating said switching means, a temperature responsive operating arm, a link pivoted on the end of one of said arms, an over-center tension spring connecting the movable end of said link with the end 01' the other of said arms, stops for limiting the movement of said link so that movement of said operating arm in response to temperature causes said link to snap from one position to another and thereby actuate said switch arm between closed and open circuit positions, resilient stop means for limiting normally the movement of said switch arm by said spring to a normal open circuit position and yielding to provide for continued movement of said switch arm to a defrost open position, a spring opposing movement of said operating arm in response to an increase in temperature, a knob connected to vary the force applied by said spring upon rotation of said knob,

'a projection on said knob, an extension on said switch arm in position to be engaged by said projection when said knob is turned to a position 01' increased force applied by said spring thereby to move said switch arm to said defrost open position whereby said link is snapped to its open circuit position, and auxiliary spring pressed means engaged by said operating arm when said arm moves to snap said link and said switch arm to their closed circuit positions.

13. A refrigerator control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement of said operating member in response to an increase in temperature, resilient stop means for limiting normally the movement of said switch member in each direction to predetermined normal open circuit and closed circuit positions, said stop means being arranged to yield to provide for movement of r d switch member beyond each of said normal positions to an abnormal position in which increased movement of said operating member is required to snap said switch member to its other normal position, a spring opposing movement of said operating member, manually operated means for varying the force applied by said spring and for moving said switch member to either one of said abnormal positions.

14. A refrigerator control device comprising a switch member, a, temperature responsive operating member, a spring forming an operating con nection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement of said operating member in response to changes in temperature, resilient stop means for limiting normally the movement of said switch member in each direction to predetermined normal open circuit and closed circuit positions, said stop means being arranged to yield to provide for movement oi. said switch member beyond each of said normal positions to an abnormal position in which increased movement of said operating member is required to snap said switch member to its other normal position, a spring opposing movement of said operating member, manually operated means for varying the force applied by said spring and for moving said switch member to either one of said abnormal positions, and auxil- 'iary spring means engaged by said operating member when said operating member is moved to snap said switch member from either one of said abnormal positions.

15. A refrigerator control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement oi. said operating member in response to changes in temperature, resilient stop means for limiting normally the movement of said switch member in each direction to predetermined normal open circuit and closed circuit positions, said stop means being arranged to yield to provide for movement of said switch member beyond each of said normal positions to an abnormal position in which increased movement of said operating member is required to snap said switch member to its other normal position, a spring opposing movement of said operating member, a knob connected to vary the force applied by said spring upon rotation of said knob, a plunger mounted on said knob for movement independently of said knob selectively inward or outward, and an oper-- ating connection between said plunger and said switch member providing for rotation of said plunger with said knob and for movement of said switch member to said abnormal positions selectively upon inward or outward movement of said plunger.

16. A refrigerator control device comprising a switch member, a temperature responsive operating member, a spring forming an operating connection between said members thereby to snap said switch member between an open circuit position and a closed circuit position upon movement of said operating member in response to changes in its temperature, resilient stop means for limiting normally the movement of said switch member in each direction to predetermined normal open circuit and closed circuit positions, said stop means being arranged to yield to provide for movement of said switch member beyond each of said normal positions to an abnormal position in which increased movement of said operating member is required to snap said switch member to its other normal position, a spring opposing movement of said operating member, a knob connected to varythe force applied to said spring upon rotation of said knob, a plunger mounted on said knob for movement independently or said know selectively inward or outward, an operating connection between said plunger and said switch member providing for rotation of said plunger with said knob and for movement of said switch member to said abnormal positions selectively upon inward or outward movement of said plunger, and auxiliary spring means engaged by said operating member when said operating member is moved to snap said switch member from either one of said abnormal positions, thereby to require abnormally high and low temperatures of said operating member for operation of said switch member from either one of said abnormal positions.

1'7. A control device comprising a switch member mounted for movement between two positions, first and second stops spaced apart in the direction of movement of said switch member, a third stop on said switch member for engaging said first stop upon movement of said switch member in one direction thereby to limit the position of said switch member to a predetermined normal first position, temperature responsive means, an operating connection between said temperature responsive means and said switch member requiring movement of said temperatureresponsive means varying in amount with the position of said switch member in said one direction in order to move said switch member from said first position to the other of its positions, a resilient mounting for .at least onev of said first and third stops, and a manually operated member movable to forcibly move said third stop past said first stop into engagement with said second stop whereby said switch member is given an abnormally great movement in said one direction requiring, an abnormally great movement of said temperature responsive means to move said switchrmember to its other position, said third stop thereafter engaging said first stop upon'a subsequent movement of said switch member in said-one direction.

18. A control device comprising a switch member movable between open circuit and closed circuit positions, two stops spaced apart in the direction of movement of said switch member, a resilient extension on said switch member for h 7 engaging upon opening movement of said switch member a nearer one of said stops thereby to limit the open circuit position of said switch member to a predetermined normal position,

temperature responsive means, an operating connection between said temperature responsive means and said switch member,requiring movement of said temperature responsive means varying in amount with the open circuit movement of said switch member in order to move said switch member to its closed circuit position, and a manually operated member movable to engage and forcibly move said resilient extension past said nearer stop into engagement with the other of said stops whereby said switch member is given an abnormally great movement in said open circuit direction requiring an abnormally great movement of said temperature responsive means to move said switch member to its closed circuit position, whereupon said resilient extension resumes its normal shape to engage said nearer stop upon a subsequent opening movement of said switch member.

EDGAR H. AYERS. 

